Method and apparatus for removing a fouling substance from a pressured vessel

Abstract

Vessels can be become fouled due to normal operation thereof, for example, during lignocellulosic biomass hydrolysis, and the vessel will become inoperable unless the fouling is removed from the vessel. Accordingly, methods are disclosed herein for removing fouling substances from the interior surfaces of fouled pressurized vessels. The methods utilize a brief rapid change of pressure in the vessel. In some embodiments, the rapid pressure change is a decrease, and the rapid pressure change causes, for example, increased velocity of the fluid flowing in the vessel, flashing of a portion of the fluid to vapor, and removal of the fouling substance adhered to the interior surface of the vessel.

What is claimed is: 
     
       1. A method comprising:
 providing a first pressurized vessel having an interior surface; 
 contacting the interior surface of the first pressurized vessel with a first fouling fluid;
 wherein:
 the first pressurized vessel has a first pressure at a first position inside the first pressurized vessel; and 
 the first fouling fluid has a first velocity at the first position; 
 
 
 depositing a first fouling substance originating from the first fouling fluid on at least a portion of the interior surface of the first pressurized vessel, thereby forming a fouled first pressurized vessel having a second pressure at the first position, wherein the first fouling fluid has a second velocity at the first position; 
 optionally, displacing at least a portion of the first fouling fluid contained in the fouled first pressurized vessel with a first fluid that is different from the first fouling fluid; and 
 rapidly changing the second pressure to a third pressure, thereby causing the first fouling fluid, the first fluid if present, or a mixture thereof within the fouled first pressurized vessel to achieve a third velocity at the first position, wherein the third velocity is greater than the second velocity; 
 wherein the method removes a portion of the first fouling substance deposited on the interior surface of the fouled first pressurized vessel. 
 
     
     
       2. The method of  claim 1 , wherein the method removes a substantial portion of the first fouling substance deposited on the interior surface of the fouled first pressurized vessel. 
     
     
       3. The method of  claim 1 , wherein the third pressure is different from the second pressure by at least about 20% of the second pressure. 
     
     
       4. The method of  claim 3 , wherein changing the second pressure to the third pressure occurs in a first time period of less than about 10 sec. 
     
     
       5. The method of  claim 1 , wherein, the first fouling fluid, the first fluid if present, or a mixture thereof is in a state selected from the group consisting of a supercritical state, a near-critical state, a saturated state, and a subcooled state immediately prior to rapidly changing the second pressure to the third pressure. 
     
     
       6. The method of  claim 1 , wherein the first pressure is at least about 1000 psia. 
     
     
       7. The method of  claim 1 , wherein the first fouling fluid has a temperature of at least about 140° C. upon commencing the rapid change from the second pressure to the third pressure. 
     
     
       8. The method of  claim 1 , wherein the first fouling fluid comprises a material selected from the group consisting of biomass, municipal waste, fractionated biomass, hemicellulose, cellulose, cello-oligosaccharides, glucose, xylan, xylo-oligosaccharides, xylose, C 6  oligosaccharides, C 5  oligosaccharides, C 6  monosaccharides, C 5  monosaccharides, lignin, starch, lipids, proteins, polypeptides, polymers, oligomers, furfural, hydroxymethyl furfural, and any combination thereof. 
     
     
       9. The method of  claim 1 , wherein the first fouling substance is selected from the group consisting of an organic material, lignin, a polyfuran, a humin, char, a degradation product of a natural material, a degradation product of a synthetic material, ash, inorganic material, and any combination thereof. 
     
     
       10. The method of  claim 1 ,
 wherein the third pressure is different from the second pressure by at least about 20% of the second pressure; and 
 wherein the method further comprises:
 adjusting the third pressure to a fourth pressure, wherein the fourth pressure is within about 20% of the second pressure. 
 
 
     
     
       11. The method of  claim 10 , wherein the contacting, depositing, optional displacing, rapid changing, and adjusting steps are performed while maintaining a pressure of at least about 500 psia. 
     
     
       12. The method of  claim 10 , wherein the method is repeated at least once, and wherein at least about 20 seconds elapse between subsequent rapid changing steps. 
     
     
       13. The method of  claim 1 , wherein the displacing step is performed. 
     
     
       14. The method of  claim 13 , wherein the first fluid comprises hot compressed water. 
     
     
       15. The method of  claim 13 , wherein:
 the third pressure is different from the second pressure by at least about 20% of the second pressure; and 
 the method further comprises:
 adjusting the third pressure to a fourth pressure, wherein the fourth pressure is within about 20% of the second pressure; and 
 supplanting the first fluid with a third fouling fluid that has a composition that is the same as or different from a composition of the first fouling fluid. 
 
 
     
     
       16. The method of  claim 15 , wherein the method is repeated at least once, and wherein at least about 20 seconds elapse between the rapid changing step and the adjusting step. 
     
     
       17. The method of  claim 1 , wherein the method does not employ an exogenous compound in an amount effective to remove a substantial portion of the fouling substance deposited on the interior surface of the fouled first pressurized vessel, wherein the exogenous compound is selected from the group consisting of an acid, a base, an organic solvent, and any combination thereof. 
     
     
       18. The method of  claim 1 , wherein the first fouling fluid, the first fluid if present, or a mixture thereof is transported continuously through the vessel. 
     
     
       19. The method of  claim 1 , wherein the second velocity changes to the third velocity at an acceleration of at least about 0.3 m/s 2 . 
     
     
       20. The method of  claim 1 , wherein the second pressure is rapidly changed to the third pressure at a rate of at least about 100 psi/sec. 
     
     
       21. The method of  claim 1 , wherein rapidly changing the second pressure to the third pressure comprises a decrease in pressure. 
     
     
       22. The method of  claim 1 , further comprising:
 providing a second pressurized vessel having an interior surface; 
 contacting the interior surface of the second pressurized vessel with a second fouling fluid; 
 wherein:
 the second fouling fluid has a composition that is the same as or different from a composition of the first fouling fluid; 
 the second pressurized vessel has a fifth pressure at a second position inside the second pressurized vessel; and 
 the second fouling fluid has a fourth velocity at the second position; 
 
 depositing a second fouling substance originating from the second fouling fluid on at least a portion of the interior surface of the second pressurized vessel, thereby forming a fouled second pressurized vessel having a sixth pressure at the second position and a fifth velocity at the second position; 
 wherein the second fouling substance is the same as or different from the first fouling substance; 
 optionally, displacing at least a portion of the second fouling fluid contained in the fouled second pressurized vessel with a second fluid that is different from the second fouling fluid; and 
 rapidly changing the sixth pressure of the second fouled pressurized vessel to a seventh pressure, thereby causing the second fouling fluid, the second fluid if present, or a mixture thereof within the fouled second pressurized vessel to achieve a sixth velocity at the second position, wherein the sixth velocity is greater than the fifth velocity; 
 wherein the process removes a portion of the second fouling substance deposited on the interior surface of the fouled second pressurized vessel; 
 wherein depositing the second fouling substance on at least a portion of the interior surface of the second pressurized vessel is performed at substantially the same time as rapidly changing the second pressure to a third pressure within the fouled first pressurized vessel. 
 
     
     
       23. The method of  claim 22 ,
 wherein displacing at least a portion of the second fouling fluid with a second fluid is performed; and 
 wherein the second fluid comprises hot compressed water.